A normal web developer just doing a simple applications including just routing and crud operations may not find much of the application. But when it comes to complex applications say finance and banking applications, web based Algo-trading platforms and some data intensive applications you may find a lot of applications esp trees, heaps, dynamic programming etc. Obviously, no one is going to tell you make a heap and pull out min element etc. It is just that more intuitive you are, more efficient will your application be because you will be able to choose correct approach to tackle a problem instead of rookie approach that may be much more time consuming.